1. Field of the Invention
The present invention relates to a camera which is capable of performing photometry on the photographic field by dividing it up into a plurality of regions and of calculating an exposure value based upon the photometric outputs from these regions.
2. Related Background Art
Recently more and more cameras have been produced which perform a so called divisional photometry method. With this divisional photometry method, photometry is performed by dividing the photographic field into a plurality of regions, and a photometric signal is obtained for each of these regions; and, for this method, the photometric element (typically a photoelectric conversion element) is divided into a plurality of sub-elements which correspond to the above described plurality of regions on the photographic field. Further, an exposure value is calculated based upon the output photometric signals for the various regions, so that photography of the principal object to be photographed can be performed with appropriate exposure settings, without the illumination level of the background exerting any effect.
With this type of divisional photometry method, the greater is the number of sub-elements into which the photometric element is subdivided, the greater is the resolution which can be obtained for the distribution of illumination over the principal object to be photographed and the area surrounding it, and accordingly the more appropriate is the exposure value which can be calculated; and therefore in recent years this number of sub-elements has increased steadily up to the range of several tens, and in the near future it is expected that in some devices the number of sub-elements will be in the range of several hundreds. For examples, reference should be made to Japanese Patent laid-open Applications Nos. 4-215631 and 4-251230.
However, with such a divided method of photometry as described above, if the position within the camera of the photometric sensor on which the light coming from the photographic field should fall has not been set accurately, then a proportion of the light emanating from the photographic field does not reach this photometric sensor, and deviation occurs between the divided photometric regions on the photographic field and the divided sub-elements of the photometric sensor which correspond to these photometric regions, so that an accurate photometric result for the object to be photographed cannot be obtained. In this connection, in the prior art, as shown in FIG. 11 of the drawings, the photometric sensor (denoted as 25) has been fixed to the body of the camera by a position adjusting construction which can provide fine adjustment both in the up and down directions and in the left and right directions. Thereby, the position of the photometric sensor 25 can be finely adjusted both upwards and downwards and also leftwards and rightwards, and can be set to correspond accurately to the position of the light emanating from the photographic field.
In more detail, referring to FIG. 11, in this prior art the photometric sensor 25 is fixed to a first support plate 203, and this first support plate 203 is fixed to a second support plate 202, which itself is fixed to a support base 201. These constructions are built so as to be adjustable, in the following manner. Two slots 203a are formed through the first support plate 203 and extend in the direction denoted as "A" in the figure (which corresponds to the up and down direction when the camera is being used for photography), and two bolts 205 are passed through these slots 203a and are threaded into bolt holes (not particularly shown in the figure) formed in the second support plate 202. Thereby, when these two bolts 205 are tightened up, the first support plate 203 and the photometric sensor 25 cannot move with respect to the second support plate 202 in any direction; but, when the two bolts 205 are loosened somewhat, first support plate 203 and the photometric sensor 25 can be slid with respect to the second support plate 202 in the direction "A", but cannot be moved in the direction "B" perpendicular thereto. Similarly, two slots 202a are formed through the second support plate 202 and extend in the direction denoted as "B" in the figure (which corresponds to the left and right direction when the camera is being used for photography), and two bolts 204 are passed through these slots 202a and are threaded into bolt holes (not particularly shown in the figure) formed in the support base 201. Thereby, when these two bolts 204 are tightened up, both of the support plate 202 and 203 and the photometric sensor 25 affixed thereto cannot move with respect to the second support plate 202 in any direction; but, when the two bolts 204 are loosened somewhat, both of the first support plate 202 and 203 and the photometric sensor 25 affixed thereto can be slid with respect to the support base 201 in the direction "B", but cannot be moved in the direction "A".
However, the larger is the number of sub-elements into which the photometric sensor 25 is divided, the more strictly must the above described position adjustment process for the photometric sensor 25 be performed; and the problem arises that this position adjustment process takes a long time and is troublesome. Further, when the photometric sensor is fixed to the body of the camera via this type of position adjusting construction, it is not possible to be absolutely confident that the photometric sensor is solidly fixed in place, and there is a danger that its position may gradually change due to the effects of shock and vibration upon the camera or over the passage of time, in which case it may become impossible to perform accurate photometry.